Feature
University plant biologist George Weiblen, lead organizer of the Evolution 2008 conference, says there has been no more exciting time to be an evolutionary biologist than today.
An evolving science
The Evolution 2008 conference celebrated a vibrant field
By Deane Morrison
June 30, 2008
On a balmy summer night, lawns come alive with the cricket
version of "American Idol," as each male "sings" in an effort to
convince the local females to pick him. In the air, male fireflies
flash to advertise their virility, looking for a female to signal
by flashing back. Besides being delightful, these ordinary mating
displays illustrate some of the myriad facets of evolution that
took center stage in the Evolution 2008 conference, held at the
University of Minnesota in Minneapolis June 20-24. It was held here
"because we have a critical mass of evolutionary biologists at the
University," says George Weiblen, an associate professor of plant
biology and lead conference organizer. "It was an opportunity to
showcase our talents and bring hot science to our doorstep. It's
the largest meeting of evolutionary biologists in the world." More
than 1,400 biologists from 22 countries, including 69 University
faculty and students, presented their research and ideas.
Siren songs, flagrant flashers, diabolical
deceit
In Hawaii, new species of crickets are rapidly evolving, said
Cornell University researcher Chris Wiley. But as new species
arise, they have to avoid interbreeding in order to remain
separate. The best way to keep separate is for males to evolve new
songs (or chirps), and for the females to evolve a preference for
that song at the same time. But why should both the song and the
preference for it evolve at the same time? It seems like a too
convenient coincidence. But maybe not.
"When we have a predator-prey system or a
host-parasite system, we have a co-evolutionary arms race where the
prey is under pressure to come up with new ways of eluding the
predator, then the predator adapts."
It could be, said Wiley, that changes--called mutations--in a
single gene or group of genes could be responsible. In a male, the
change results in a new song, while in the female the change
confers a preference for that song. Sometimes, one gene can produce
different traits in males and females, and Wiley and his colleague
Kerry Shaw are investigating whether this is happening in the
crickets. A recurring question in evolutionary biology is how new
versions of old genes arise in the first place. Researcher Yuichi
Oba (Nagoya University, Japan) reported on his studies of genes
found in fireflies and other beetles; his work suggests a likely
way in which genes for the flashing ability first appeared and then
diversified, resulting in different flashing patterns in different
firefly species.
A new look at the history of
evolution
The theory of evolution has had its share of both fans and critics
over the centuries. In a new book, "More Than Darwin: An
Encyclopedia of the People and Places of the Evolution-Creationism
Controversy (Greenwood Press, 2008)," University authors Randy
Moore and Mark D. Decker lay out the life and times of one of the
greatest ideas in all science, with sketches of the often colorful
characters who promoted or condemned it. Moore is the H.T.
Morse-Alumni Distinguished Teaching Professor of Biology and Decker
is associate director for scholarship and teaching in the Biology
Program.
Listen
to an interview with Randy Moore about writing the book.
The firefly owes its flash to an enzyme known as luciferase, which
carries out a chemical reaction that produces light. Oba found
intriguing similarities in genes for luciferase and genes for an
enzyme that metabolizes fatty substances; this second enzyme is
found in both fireflies and related beetles. Most probably, said
Oba, a genetic error occurred long ago in a beetle. That error
caused the gene for the fat-metabolizing enzyme to be duplicated.
The extra copy of the gene that could then mutate without harming
the original gene's function. As the beetle's descendants
multiplied, the extra gene mutated into the gene for luciferase,
and fireflies were born. But evolution doesn't stop. As befits
insects with an enzyme named for Lucifer, some fireflies have
evolved the ability to put their flashes to diabolical use. Certain
females can mimic the flashing patterns of females of other
species. On seeing those flashes, amorous males of the other
species fly straight to the source, where they are promptly
devoured.
The better to kill you with, my deer
A study of wolves in Yellowstone Park led by University postdoc
Daniel MacNulty shows that as predators evolve to take the prey
available, sizing themselves can be a tricky thing. "Species within
lineages tend to evolve into larger sizes," said MacNulty, using
the diminutive ancestors of modern whales, horses, and elephants as
examples. "Bigger predators chase bigger prey, but bigger size can
slow them down." The Yellowstone wolf packs used different skills
to bring down elk, MacNulty reported. First they rush the herd,
then they select an individual and separate it from its fellow elk,
and finally they wrestle it to the ground and kill it. Rushing
doesn't seem to require any particular size, MacNulty said, but
closing in on the chosen victim requires a burst of speed, which
would be hampered by too much body weight. Conversely, pulling the
elk down is a job for burly wolves. In fact, MacNulty and his
colleagues found that a wolf's chances of successfully separating
an elk out from the herd rose only until the wolf reached about 86
pounds, then leveled off. But the chances of wrestling down and
killing an elk didn't level off, suggesting that large size is
favored for this job. Size is a tradeoff; male lions, for instance,
are bigger than females and worse at chasing prey but better at
killing, he said. In general, small carnivores, such as cheetahs,
are adapted to running while large ones, such as polar bears, are
built for grappling. According to fossil evidence, "extinctions of
American lions [larger Ice Age cousins of sabretooth cats] may
suggest they couldn't shift from larger, slow prey [like mammoths,
which went extinct] to smaller, faster prey," said MacNulty.
The Red Queen lives
In Lewis Carroll's "Through the Looking Glass," Alice meets the Red
Queen, who must run as fast as she can just to stay in place. The
Red Queen has been adopted as a metaphor by some evolutionary
biologists to illustrate how predators and prey have to keep up
with each other. "When we have a predator-prey system or a
host-parasite system, we have a co-evolutionary arms race where the
prey is under pressure to come up with new ways of eluding the
predator, then the predator adapts," says Weiblen. "A good example
of the Red Queen is the pharmaceutical industry and infectious
bacteria. New antibiotics like streptomycin come along, and
bacteria evolve resistance." A strong driving force in such systems
is natural selection, which means that bacteria in which
antibiotic-resistance genes appear will be "selected" to live and
give rise to the next generation Given that, plus numerous
observations that people differ considerably in their resistance to
disease, their response to drugs, and other traits, Weiblen calls
on the University to add evolutionary biology to its Medical School
curriculum. "The ability to care for our bodies is enhanced by
knowing our history as a species," he says. "The medical profession
isn't aware of evolutionary biology's potential for making them
better doctors," adds Scott Lanyon, director of the University's
Bell Museum of Natural History. "Evolutionary biologists in general
feel strongly [that there's a real need to integrate evolutionary
biology into medical curricula."